CVE-2026-41210

What it is

Moonlight Qt is a GameStream client for Windows, macOS, Linux, and Steam Link. In version 6.1.0 and earlier, after a victim initiates a streaming session to a malicious host, the host can send a crafted H.264 SPS NAL when Moonlight selects a decoder path that does not advertise CAPABILITY_REFERENCE_FRAME_INVALIDATION_AVC. The SPS fixup path in app/streaming/video/ffmpeg.cpp parses the server-provided data with h264bitstream, where attacker-controlled seq_parameter_set_id is used to index the 32-entry sps_table without validation. A value of 32 or greater causes an out-of-bounds write and remote heap corruption in the Moonlight client. The demonstrated impact is a reliable client crash, while code execution is not established. This issue is fixed in version 6.2.0.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. High risk of service disruption.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-10-12 22:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-16 20:04 UTC Last updatedMost recent change to the record

Details

Published

2026-10-12 22:17 UTC

Last modified

2026-10-16 20:04 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-787 · Out-of-bounds write

Record status

Deferred

Attack profile CVSS 3.1 · 6.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High